Mild Winter Temperatures Could Spark Nematode Activity

Clint Thompson Field Crops

Cotton roots infected with root-knot nematodes swell in response to the infection. These knots serve as feeding sites where nematodes (microscopic worms) grow, produce more eggs and stunt the plant’s growth. (UGA)

By Clint Thompson

Temperatures this winter have been abnormally mild, which could be a problem for row crop farmers when they begin planting this year’s crop. The lack of freezing temperatures is likely to spark nematode activity, and Bob Kemerait, University of Georgia Cooperative Extension plant pathologist, encourages all producers to be prepared.

Southeast AgNet’s Clint Thompson talks with Bob Kemerait about nematodes.

“I’m telling growers I’ve had to break the ice out of my dog’s dish twice this year. That tells me we’ve not had real cold weather. The colder the weather, the better for managing nematodes. It sends them into a hibernation phase,” Kemerait said.

Colder weather helps protect farmers from nematodes in two ways. Freezing temperatures help kill off any regrowth in cotton and corn fields, volunteer peanuts or unintentionally planted peanuts and weeds — all of which serve as host plants for nematodes. Also, if soil temperatures get below 50 degrees, nematodes quit being active. Root-knot nematodes might exist only in egg form. Some reniform and other types of nematodes slow down in colder temperatures and are metabolically inactive.

Unfortunately for producers in the Southeast, freezing temperatures have almost been nonexistent this winter.

“What does that translate into for 2020? Growers need to recognize that the winter has not helped them a whole lot; probably hurt them more than helped them. They need to recognize we may have more of a nematode problem coming into 2020 because of that,” Kemerait said.

Nematodes are microscopic, worm-like pests. Root-knot nematodes cause the most problems for cotton farmers. They feed on cotton roots and cause swelling, or “galls,” to develop. The galls disrupt the function of the roots, which stunts the plant’s growth.

Though growers might be tempted to take nematode samples, Kemerait advises against that since growers may not get accurate information. If the sample reports a lack of nematode activity, the producer doesn’t know if it’s due to being a wintertime sample or if the nematodes weren’t there to begin with.

Kemerait stresses to growers to consider nematode-resistant varieties when possible. Resistant varieties sustain minimal damage from the nematodes and minimize their buildup.

“What I’m telling growers is, regardless of what crop you’re planting, if it’s cotton, peanuts, or if it’s soybeans, are there root-knot nematode-resistant varieties you can consider? Are there some reniform-resistant varieties you might consider on soybeans? If there are, will they work in your schedule?” Kemerait said. “But if you’re going into a situation where you’re worried about nematodes and not exactly sure there was a problem and not going to use a nematode-resistant variety, you need to think about what you’re going to do as far as nematicides.”

About the Author

Clint Thompson

Multimedia Journalist for AgNet Media Inc.